Simple Approach of Negative Testing

Multiple clients have sought out Nascenia due to customer frustration caused by system errors. Negative testing can help prevent this from occurring. 

In the current digital space, a slight glitch or system crash in applications can cause your users to become dissatisfied and eventually cost your reputation in the long term. To solve these recurring issues, you need to prioritise testing. When we talk about testing, multiple types can be utilised, and among them, negative testing plays a critical role. 

Negative testing works by deliberately challenging the platform with unexpected inputs to observe the response. The goal of this approach is not to break the software environment – instead, it ensures the system fails safely and can recover gracefully. Whether you launch a new website or scale an existing one, you must cover all your bases by utilising negative testing as part of your Quality Assurance (QA) strategy. 

Read on to find out more about negative testing, why it’s so crucial, typical scenarios where it can be applied, and how you can implement it using various tools and techniques. 

Types of Software Testing

Generally, the QA team would be aware of several types of testing, such as functional, unit, integration, regression, performance, security, alpha, beta, etc. However, all these categories are primarily divided into two main types, Positive and Negative Testing.

Positive Testing

Determines that the application meets functional requirements. If an error has occurred during this process, the corresponding test case will fail.

Negative Testing

Negative Testing is also known as failure testing, error path testing, or fault injection testing – the aim is to find how the framework responds to incorrect inputs or information. Negative testing tries to understand the stability of the program when customers are most likely to make mistakes.

Importance of Negative Testing

Negative testing helps ensure that applications can carefully respond to malformed entries or unexpected user behavior outside of the expected flow. For example, if a user tries to type a letter in a numeric field, the correct behavior for the software would be to display a message such as “Invalid data type, please enter a number”. 

The purpose is to detect common misinputs and prevent applications from crashing. It can also be used to identify major validation or verification failures in specific parts of the platform. Lastly, failure testing helps us to improve the quality of the application and find its weak points.

Typical Negative Testing Scenarios

Below are several possible examples of such situations:

1. Mandatory Data Entry

Some fields are mandatory to submit a form in a web or desktop application. The development team will try to submit it by not filling up one or more mandatory fields to see what happens.

2. Field Type Test

Software specification indicates different fields of several data types – date fields, numeric fields, phone numbers, zip codes, and more. For instance, Alphabetic should not allow numeric values, numeric values must not allow alphabetic or special characters, date fields require a valid date, etc. 

3. Field Length Test

The documentation usually outlines the character limits for each field, both maximum and minimum thresholds. There should be validation checking where the development team checks for fields larger than the maximum length and smaller than the minimum. 

For example, if the specification mentions that the maximum length of a text input field is 32 characters, then 33 characters ought to be tried. Similarly, if the minimum length is 6 characters, then the QA engineers are expected to test it with 5 characters.

4. Boundary Values Test

The Boundary Value Analysis technique allows the identification of the appropriate number of input values; reveals how tolerant your platform is towards extreme values. For example, a numeric text field accepts a value from 10 to 100. So, the QA team should test it out of its boundary values, by 101 and 9, i.e. maximum of its higher boundary and the minimum of its lower boundary value. 

5. Date Validity

It is important to guarantee that invalid dates are not allowed. For instance, entering 31/09/2015 (invalid date) needs to be flagged immediately. Developers are also advised to check for leap years. For example, February must not have 29 days if the year is not a leap year.

6. Embedded Single Quote

End-users can store information with a single quote for alphanumeric data in SQL-based systems. This can generate issues. QA engineers should try different input fields with text that contains one or more single and double quotes.

7. Web Session & Cookies Testing

Cookies are small text file that gives ID tags that are stored in our computer’s browser directory or program data. To maintain the session, cookies are used. The testing team must test the application by enabling or disabling cookies in the browser options.

8. Performance Changes With Stress And Concurrent Testing

The development team should extend performance testing beyond functional testing.

Important performance tests are:

• Load testing
• Stress testing
• Concurrent testing

For example, a get or post request works successfully for a single request, but the application changes after a certain time for a huge request. Testers must identify the maximum request threshold and the point at which it crashes or fails to send responses. The QA team should also test its behavior for concurrent requests.

Difference between Positive and Negative Testing 

Now, we cannot talk about negative testing without mentioning the other side of the coin. Positive testing basically checks if the programmed functions are working as intended. This approach assumes that end-users will interact with the platform correctly, with no unexpected behavior. 

The table shows some differences between the two:

Features	Positive Testing	Negative Testing
Objective	The system operates as expected with valid inputs	Check system behavior with invalid or unexpected inputs
Assumption	Users behave correctly	Users make mistakes or behave unexpectedly
Input Type	Valid data	Invalid or unexpected data
Issue Discovery	Detects expected failures	Detects unexpected failures
Complexity	Easier to design and interpret	Can be more complex, requires a creative scenario
Use Case	Simple applications or modules	Complex systems need robustness

Benefits of Negative Testing

• Debugging software: Failure testing is a great way to identify anomalies, helping developers to debug them easily.

• Covers a wide range of issues: Because of how many ways one can interact with the framework incorrectly, a lot of issues show up due to this test, which can help fix a lot of problems one would not even think about during the creation stage. As a result, a lot of unforeseen issues can be solved.

• Enhances user experience (UX): User experience (UX) is one of the most crucial aspects of any software. Negative testing can help find faults within the user interfaces and help rectify them to ensure a quality product for end-users.

Limitations of Negative Testing

• Extra cost and time: As you can tell, negative testing will take up more time and money to conduct. As the issues will be unforeseen, it can drive up the costs required to fix them. Depending on the complexity of the program, it can also be very time-consuming, and oftentimes not worth the effort.

• Not appropriate for all projects: Error path testing is more suited for complicated projects. It may not be worthwhile to conduct one for programs with simple functionalities. Some programs, like blogs and info sites, make extensive testing unnecessary, as they might not even require customer input

• Skilled programmers required: Negative testing is a difficult task that not just any programmer can handle. You will need skilled and experienced professionals to properly conduct and handle the workload.

When to Perform Positive vs. Negative Testing?

Going through the properties of both tests, we can safely say that positive testing is more suited for simple programs. Your application may require little input from users, or the chances of input errors are drastically low. In such cases, run a positive test to check if your program is working properly, and then proceed to launch.

If you are working with a complex application and/or need maximum stability, a negative test is the way to go. This will help you discover unintended errors and defects, and cover weaknesses you did not think of. Sure, it can be time-consuming, as mentioned before, but it is a necessary process for any crucial program.

How to Conduct Negative Testing (Steps)

Negative testing lets you assess how your framework responds to unexpected or unsupported entries. 

Here are the steps to follow while conducting negative testing: 

1. Define Negative Test Cases: You have to define test cases or scenarios based on potential failure points. Make sure you include invalid inputs, security-related scenarios, and out-of-bound values.  Basically, consider all sorts of scenarios where users can perform unauthorized actions. 

Example: If a field accepts numbers between 1 and 100, then numbers outside that range, like 0, 101, or non-numeric input like abcd, are candidates.

1. Determine Input Conditions: Identify all the available fields and inputs that are just outside the acceptable range – ones that the system will reject. 

• Date format: If the system expects a date in the form of “YYYY-MM-DD,” try “DD-MM-YYYY” format instead.
• Required field: Leave mandatory fields empty 
• Name field: See if long names that exceed the character limit are allowed 
• Data type: Say if a field expects numbers only, try inputting 123hskd 

1. Prepare the Test Environment: Your testing environment needs to be set up in a way that mimics the production environment – configure test data, user roles, and permissions. A controlled environment helps to minimise the risk of affecting the actual system.. 

• Use Manual or Automation Tools to Test: Run your failure test scenarios using manual or automated tools; use automation tools like Selenium or TestNG to simulate inappropriate values. Carefully observe the application behaviour, response time, logging, or alert triggers. 

1. Monitor Unexpected Behavior: Pay attention to how the platform handles input during testing – check for issues like errors, unhandled exceptions, or data corruption. Capture logs, error messages, and system responses to verify that the software environment behaves as expected when handling failures. 
2. Analyze Errors and Report Issues: Analyze the results to ensure that the system responds with useful feedback. For instance, rather than showing “Error 500”, the system should show a helpful message like “Invalid input, please enter a number between 1 and 100”. 

Document all the findings and share the issues with the development team, who will further investigate the root causes and carry out fixes.

1. Repeat the Process: Retest the negative test cases to confirm that all the faults have been resolved and no new issues crop up due to the new changes – this is called regression testing. 

Tools for Negative Testing

Unit Testing

Unit testing involves verifying individual components of the code to find out if they are functioning properly or not. It is a tool that can be used to conduct both positive and negative tests. Normally, unit testing is done by developers as they are creating software. It can be difficult to properly unit test products, as individually verifying each component can be very laborious. Tools such as Selenium, Cypress, TestNG, and more can help with unit testing. 

End-to-end Testing

End-to-end testing involves using the platform in its final version as it is being developed; tools like Playwright and Katalon Studio can be utilised. Just like unit testing, this helps identify issues early in the development process, where they can be taken care of in a timely manner. Some common scenarios are running the whole system during development, performing common tasks, and forcefully shutting down the program.

Security Testing

Security tests involve trying to breach the framework with common tactics to find “cracks” in the system and dealing with them. Common hacking tools like Burp Suite, Nmap, and OWASP ZAP are utilized to ensure the smooth running of this test. 

Test with Nascenia 

Negative testing is a great tool to find and cover weaknesses in your application. Unlike traditional tests, negative test scenarios reveal flaws and ensure that the software is ready for end users. Hopefully, this article has provided you with insights into why you may or may not want to run negative tests. 

If you require more information that is specific to your situation, feel free to contact us. Our team of experts is ready to guide you in creating reliable, user-friendly software.